Video is a series of frames (still images) captured in rapid succession. Video may be recorded, displayed, stored and/or transmitted by progressive scanning or interlaced scanning Progressive scanning is where all the lines of each frame are drawn in sequence. Interlaced scanning is where each frame is divided into 2 fields one containing all the even lines of the frame and one containing all the odd lines.
Television broadcasts are typically captured using interlaced scanning The rate depends on the television broadcast standard adopted. For example, the National Television System Committee (NTSC) standard is 60 fields/sec (30 frames/sec). Older cathode ray tube (CRT) displays were able to display interlaced video based on their complete analog nature. However, current displays, such as liquid crystal displays (LCD), digital light processing (DLP), and plasma are inherently digital in that the display includes discrete pixels and therefore can not display interlaced video. Accordingly, these displays need to combine the even and odd fields into a single frame for display. However, as the fields of the frame were shot at different times simply combining the images will result in various visual defects. A de-interlacing process is needed for the display to create a progressive scanning video from the interlaced video that limits the visual defects.
Motion pictures (movies) are typically captured on 24 frames (still images) per second film using progressive scanning A process known as “telecine” may have been used to convert the motion picture from the format of 24 frames per second to the 60 fields per second rate utilized by an NTSC broadcast television network. The telecine process includes repeating frames according to a certain pattern, known as a pull-down pattern, to convert the 24 frames to 60 fields. In order to present the movies on a display without affecting the quality of the original 24 progressive frames, the display needs to perform an inverse telecine operation to reverse the pull-down pattern and discard the repeated frames.
A display may receive interlaced video or video with various telecine pull-down patterns (various film modes). The display therefore needs to be capable of performing de-interlacing and inverse telecine operations. In order to know what operations need to be performed on the received video, the display needs to determine the film mode of the video. If a display incorrectly indentifies the film mode of the video, the wrong processing may be performed on the video. For example, if the display processes a telecine video as an interlaced video or processes a telecine video with the wrong inverse telecine operations the video presented on the display may have visual defects (e.g., lost detail, combing artifacts).